Cam Plug O Rings
 

I have a 98 Montero Sport V-6 4wd. I've been told that I need to replace the O rings on the cam plugs. I' m a novice at car repair. Is this a difficult task? I would like to attempt myself to save money? Tips, procedures, advice would be greatly appreciated.

Easy to DIY.

Get:
O-rings from the dealer - approx $2.50 each some years ago - may be more now.
Small (1/4") ratchet drive
12, 13 or 14 mm short socket (can't remember which)
Spray brake cleaner
Tube of good RTV sealant.

Start on the passenger side - easiest to get to. Feel around the rear of the cylinder head facing the firewall. You will find an approx 2" circular recess surrounded by a football shaped flange with two bolts on either end of the football.

Use the socket to remove the bolts and a small screwdriver to pry out the plug and flange. You will see the old (flattened) o-ring. Replace it with the new one and use the brake cleaner to clean all mating surfaces. It's not in the book but I used the RTV sealant to smear a thin layer on the mating surfaces. Then insert the "plug" and replace the bolts. Passenger side done!

Driver's side is exactly the same but when you try to get your hand in there you'll find it's much harder to get to. Here are some tips.

Use vice grips or a hammer to bend the engine lifting hook out of the way towards the front of the truck.

Unbolt the clamps holding the A/C lines to the firewall so you can move them a bit.

Wrap a rag around the spring clips in the fuel lines and wrap with masking tape. This will prevent you from getting your hand shredded when you reach in to remove the bolts.

Final problem: When you finally are able to reach in and find the plug and bolts you will note that the wiring harness from the engine to the driver's side O2 sensor runs right across the cam plug and will prevent you from removing it.

I unhooked the hold down clamps and used some twine to pull the wire over towards the passenger side - thus leaving the cam seal plug free to be removed.

Once you have done this side, reattach the wire and, if you care, straighten out the lifting hook.

Then you should be good to go.

Ron

How many O-rings are there total?? Do you happen to have a schematic if possible? Sorry for the newb questions.

Just 2 - one for each side. I don't have a diagram but when you go to the dealer to buy the o-rings they can show you in the parts diagram where they go. This is probably the most common issue with these engines so they will know what you are looking for.

Get a flashlight and look at the top rear passenger side of the engine where it faces the firewall. You should be able to see/feel the flange with two bolts that need to be removed to expose the o-ring.

Ron

A couple additional tips from someone who has performed this repair many times.

1. Not applicable to the 1997-98 models, but if you have a 3.5L version, this is a lot easier than it is on the 3.0.

2. I do NOT use RTV or any sealant on the o-rings or cam plugs. Instead, I use silicone grease. Just a small amount on the o-rings. The grease does a few things. First, it makes the installation of the plug easier. Second, it helps the o-rings last longer. Third, if/when the new o-rings fail again, it makes it easier to remove the cam plugs in the future. If you RTV them in, it is a major PITA to get them off again.

Here is a useful DIY on the procedure.

http://msport97.proboards.com/index....e=1#1076922454

Hi Challenger4x4:

Thanks for the reminder - I meant to go back and clarify. I did NOT use RTV on the o-rings either - that is indeed unnecessary and causes problems later. What I meant to say (and should have clarified) is that I used sealant on the metal to metal outside mating surfaces where the plugs meet the head.

No doubt this is a redundant step but it was advised in another post I read so I did it and have not had a relapse of leaks for the last 125K miles.

Ron

Thanks guys I appreciate the help! Keep feeding me info.

Hi jrmdir,

Yes, RTV is commonly recommended by others on the mating surfaces between the cam plug and the head but I think it's a mistake. Try getting a cam plug off that has been RTV'd on previously! It's a super PITA.

Silicone grease is not an adhesive, it's a non-petroleum grease (won't eat the O-ring). From my experience it seems the help the O-rings stay pliable longer by providing some sort of environmental barrier around the O-ring, which helps them hold the seal longer. But when they do fail, and they will if you keep the vehicle long enough, the lack of any sealants or adhesives makes it easy to perform the fix again.

I personally don't think RTV on the mating surface of the cam plug is a viable alternative to a failed O-ring. I'd rather know the O-ring failed as soon as it does and fix it right away. It only takes 15 to 20 minutes unless you have to wrestle with breaking the RTV seal. But that's just my humble opinion.

Here are the o-rings the dealer sold to me for 16.50 apiece. Jeeez they sure mark it up pretty nice.

Attached is also a schematic I asked for. Where I circled it and pointed to with an arrow is where the o-rings are at correct on both sides??